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1.
Environ Microbiol ; 26(1): e16557, 2024 Jan.
Article in English | MEDLINE | ID: mdl-38173306

ABSTRACT

Marine snow and other particles are abundant in estuaries, where they drive biogeochemical transformations and elemental transport. Particles range in size, thereby providing a corresponding gradient of habitats for marine microorganisms. We used standard normalized amplicon sequencing, verified with microscopy, to characterize taxon-specific microbial abundances, (cells per litre of water and per milligrams of particles), across six particle size classes, ranging from 0.2 to 500 µm, along the main stem of the Chesapeake Bay estuary. Microbial communities varied in salinity, oxygen concentrations, and particle size. Many taxonomic groups were most densely packed on large particles (in cells/mg particles), yet were primarily associated with the smallest particle size class, because small particles made up a substantially larger portion of total particle mass. However, organisms potentially involved in methanotrophy, nitrite oxidation, and sulphate reduction were found primarily on intermediately sized (5-180 µm) particles, where species richness was also highest. All abundant ostensibly free-living organisms, including SAR11 and Synecococcus, appeared on particles, albeit at lower abundance than in the free-living fraction, suggesting that aggregation processes may incorporate them into particles. Our approach opens the door to a more quantitative understanding of the microscale and macroscale biogeography of marine microorganisms.


Subject(s)
Bays , Microbiota , Particle Size , Salinity , Oxygen/analysis , Estuaries
2.
Sci Total Environ ; 843: 156984, 2022 Oct 15.
Article in English | MEDLINE | ID: mdl-35760184

ABSTRACT

Engineered titanium dioxide (TiO2) nanoparticles (NPs) are widely used and consequently released into the environment. The subsequent accumulation of TiO2 NPs in depositional environments may affect the geochemical behavior of trace metals, which needs to be assessed. Here, we performed experiments to investigate the speciation change for molybdenum and tungsten in the presence of TiO2 NPs. Laboratory results show that the rate constant for MoS42- hydrolysis associated with TiO2 NPs is ~1.75 × 10-9 L m-2 s-1, whereas it is 5.95 × 10-10 L m-2 s-1 for WS42- hydrolysis. In addition, we estimated the maximum rate for MoS42- hydrolysis to be ~1.24 × 10-1 µM hr-1, whereas the maximum rate for WS42- hydrolysis is ~4.91 × 10-2 µM hr-1. However, the modeling results suggest that the TiO2 NPs accumulated in estuarine sediments might play a relatively minor role in affecting the speciation of trace metals prior to the current time. This is because the relatively low accumulation (i.e., < 8 × 10-3 mol kg-1) of TiO2 NPs before 2021 results in the lower rate (>100 times) for speciation changes of both molybdenum and tungsten compared to the rate for natural geochemical processes. On the other hand, our results suggest that TiO2 NPs will likely impact the oxyanion cycling in the near future owing to the increasing accumulations of TiO2 NPs in estuarine sediments.


Subject(s)
Metal Nanoparticles , Nanoparticles , Trace Elements , Molybdenum , Titanium , Tungsten
3.
Mar Pollut Bull ; 143: 134-139, 2019 Jun.
Article in English | MEDLINE | ID: mdl-31789148

ABSTRACT

The bioaccumulation and the main source of total Hg (THg) and methylmercury (MMHg) in the deposit-feeding polychaete Neanthes japonica collected in Jinzhou Bay, China, were investigated. Compared with the historical data, THg bioaccumulation in polychaetes collected in sediment of Jinzhou Bay was distinctly higher due to higher sediment THg concentration, but MMHg bioaccumulation was significantly lower. THg accumulation in polychaetes mainly derived from its accumulation in sediment. However, MMHg bioaccumulation in polychaetes did not correlate with Hg concentration in sediment. Besides sediment ingestion, MMHg accumulation in polychaetes may partially source from the process of in vivo transformation. The in vivo Hg methylation may take place in polychaetes, according to the excellent correlation between MMHg concentration and THg and inorganic Hg concentration in polychaetes. The biochemical characters in polychaete body, the oxidation-reduction environment and the microbial activity in polychaete gut may be beneficial to in vivo Hg methylation.


Subject(s)
Geologic Sediments/analysis , Mercury/pharmacokinetics , Methylmercury Compounds/pharmacokinetics , Polychaeta/metabolism , Water Pollutants, Chemical/pharmacokinetics , Animals , Bays , Bioaccumulation , China , Environmental Monitoring , Mercury/analysis , Methylmercury Compounds/analysis , Polychaeta/drug effects , Water Pollutants, Chemical/analysis
4.
Water Res ; 154: 162-170, 2019 05 01.
Article in English | MEDLINE | ID: mdl-30782558

ABSTRACT

Titanium dioxide (TiO2) nanoparticles (NPs) encounter heavy metals in the environment under different scenarios. However, the mechanism of their joint toxicity effects on Daphnia magna remains vague. This study assessed the effects of hydrophobicity of TiO2 NPs (TDONPs) and exposure scenarios on copper uptake and toxicity in Daphnia magna. In the individual exposure scenario, hydrophilic and hydrophobic TDONPs both showed no acute toxicity to Daphnia magna, whereas individual Cu2+ exposure resulted in a 30% mortality rate. Co-exposure and sequential exposure to the two types of TDONP and Cu2+ resulted in mortality rates of 40%-50%. The mechanisms of the increased Cu2+ toxicity caused by hydrophilic and hydrophobic TDONP were different. In the presence of hydrophobic TDONPs, the Cu toxicity could be attributed to the increased bioaccumulation of Cu and Ti, leading to high oxidative stress injury. The Cu toxicity due to hydrophilic TDONPs could be induced by intensified intestinal membrane damage. The obtained data suggest that the hydrophobicity of the TDONPs plays a critical role in regulating the toxicity of Cu2+.


Subject(s)
Nanoparticles , Water Pollutants, Chemical , Animals , Copper , Daphnia , Hydrophobic and Hydrophilic Interactions , Titanium
5.
Environ Sci Pollut Res Int ; 21(24): 14069-77, 2014 Dec.
Article in English | MEDLINE | ID: mdl-25047015

ABSTRACT

In this study, we measured trace metals (Cd, Cr, Cu, Ni, Pb, and Zn) in water and sediment from representative sites of Taihu Lake, with focus on the analysis of trace metal accumulation in Corbicula fluminea (bivalve). The results showed that the quality of water in Taihu Lake was generally good and the correlation was not found between Cu bioaccumulation in C. fluminea and the concentration in water and sediment. Thus, using the stable isotope tracer method, we studied Cu uptake from the water phase, the assimilation of Cu from the food phase, and the efflux of Cu in vivo by C. fluminea. The result revealed that this species exhibited a relatively lower efflux rate constant of Cu compared with other zoobenthos species. Using a simple bioenergetics-based kinetic model, Cu concentrations in the C. fluminea were calculated with the measured efflux rate. We put forward a novel method, which was taking the influence of biological kinetic on metal bioaccumulation into account to explain the field survey data.


Subject(s)
Corbicula/chemistry , Environmental Monitoring/methods , Lakes/chemistry , Metals, Heavy/pharmacokinetics , Water Pollutants, Chemical/pharmacokinetics , Animals , Biological Availability , Bivalvia , China , Geologic Sediments/chemistry , Isotopes/analysis , Metals, Heavy/chemistry , Trace Elements/analysis , Water Pollutants, Chemical/chemistry
6.
Water Res ; 46(18): 5981-8, 2012 Nov 15.
Article in English | MEDLINE | ID: mdl-22999974

ABSTRACT

Great progress has been made in the controlled fabrication of nanomaterials with given sizes, shapes, and geometries. However, how such changes in structure potentially affect the bioavailability and toxicity of metal nanoparticles to aquatic organisms remains mostly unknown. The present study reports the different behaviors of two types of Cu(2)O micro/nanocrystals (micro/nano-Cu(2)O) with different shapes (cubic and octahedral) and crystallographies (with exposed surfaces as {100} or {111}). The bioaccumulation, median lethal concentration, and biomarker responses of Daphnia magna exposed to the two micro/nanocrystals are also investigated. The Cu accumulation, production of metallothionein (MT), and inhibition ratio of D. magna increased gradually with increasing micro/nano-Cu(2)O concentration. The two crystals showed slight Cu accumulation differences toward D. magna, and their biomarker responses and toxicities to D. magna differed significantly as well. The octahedral Cu(2)O micro/nanocrystals were more toxic to D. magna compared with the cubic micro/nanocrystals probably because of the higher surface activities of the {111} facets compared with those of the {100} facets for cuprites. Food ingestion was the main entry pathway of the micro/nanocrystals into organisms, and toxicity was consequently determined based on the dissolution behavior of the micro/nanocrystals in vivo.


Subject(s)
Copper/chemistry , Copper/toxicity , Daphnia/drug effects , Nanoparticles/chemistry , Nanoparticles/toxicity , Water Pollutants, Chemical/chemistry , Water Pollutants, Chemical/toxicity , Animals , Daphnia/metabolism , Metallothionein/metabolism
7.
Environ Sci Technol ; 46(18): 10255-62, 2012 Sep 18.
Article in English | MEDLINE | ID: mdl-22894800

ABSTRACT

This study attempts to understand the impact of different shapes of an individual micro/nanomaterial on their biotoxicities to aquatic organisms. Two differently shaped Cu(2)O micro/nanocrystals (cubes and octahedrons with side lengths of 900 nm) were exposed to Daphnia magna for 72 h, afterward several antioxidant biomarkers such as reactive oxygen species (ROS), catalase (CAT), total antioxidant capacity (T-AOC), and malondialdehyde (MDA) in D. magna were measured. We demonstrated the differential influences of two crystallographic Cu(2)O nanocrystals on the antioxidant process. Specifically, octahedral Cu(2)O nanocrystals showed a higher level of oxidative stress, possibly because of its larger surface area and higher reaction activity of the octahedron. The biomarker results further showed that the oxidative stress and antioxidant mechanism process involved three stages-antioxidant response, oxidation inhibition, and antioxidant inactivation. Furthermore, the accumulation of MDA was mainly responsible for the ROS-induced toxicity.


Subject(s)
Copper/toxicity , Daphnia/physiology , Nanoparticles/toxicity , Oxidative Stress/drug effects , Water Pollutants, Chemical/toxicity , Animals , Catalase/metabolism , Copper/chemistry , Copper/metabolism , Daphnia/drug effects , Malondialdehyde/metabolism , Models, Molecular , Nanoparticles/chemistry , Nanoparticles/ultrastructure , Reactive Oxygen Species/metabolism , Water Pollutants, Chemical/chemistry , Water Pollutants, Chemical/metabolism
8.
Environ Pollut ; 159(3): 729-34, 2011 Mar.
Article in English | MEDLINE | ID: mdl-21177008

ABSTRACT

The acute toxicity of engineered nanoparticles (NPs) in aquatic environments at high concentrations has been well-established. This study demonstrates that, at a concentration generally considered to be safe in the environment, nano-TiO(2) remarkably enhanced the toxicity of copper to Daphnia magna by increasing the copper bioaccumulation. Specifically, at 2 mg L(-1) nano-TiO(2), the (LC(50)) of Cu(2+) concentration observed to kill half the population, decreased from 111 µg L(-1) to 42 µg L(-1). Correspondingly, the level of metallothionein decreased from 135 µg g(-1) wet weight to 99 µg g(-1) wet weight at a Cu(2+) level of 100 µg L(-1). The copper was found to be adsorbed onto the nano-TiO(2), and ingested and accumulated in the animals, thereby causing toxic injury. The nano-TiO(2) may compete for free copper ions with sulfhydryl groups, causing the inhibition of the detoxification by metallothioneins.


Subject(s)
Copper/pharmacokinetics , Copper/toxicity , Daphnia/drug effects , Titanium/pharmacokinetics , Water Pollutants, Chemical/pharmacokinetics , Water Pollutants, Chemical/toxicity , Adsorption , Animals , Daphnia/metabolism , Lethal Dose 50 , Metal Nanoparticles/chemistry , Metallothionein/metabolism , Titanium/chemistry
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